QF4400SU; edition 2018-11; page 16 of 19
5. Operating troubles, causes and remedial action
(Troubleshooting)
No.
Operating troubles
Causes and remedial action
Pump
does
not
start
Pump
does
not
prime
Delivery
is not
ob-
tained
or
reduced
Pressure
head is
not
obtained
Irreg-
ular
pump
delivery
Pump
oper-
ates
noisily
Pump
is
leaky
Motor
gets
too
warm
1
X
X
The screws of the pump-chamber maybe not
tightened enough. Fix it!
2
X
Check the direction of flow showed by the arrow
on the pump, in case of wrong way, turn the
pump head.
3
X
X
X
Check suction pipeline and TC- seals for
tightness.
4
X
X
X
X
Check suction head-increase suction line cross
section.
5
X
X
X
Check viscosity of liquid pumped.
6
X
Check pump speed. Control speed of drive
motor. Check voltage and frequency.
7
X
X
X
Avoid air inclusions in the liquid to be pumped.
8
X
X
Check pressure head-open valve in discharge
line completely, remove obstruction in discharge
line.
9
X
Pressure line completely or partly clogged,
diaphragm maybe broken,
change diaphragm!
10
X
The diameter of the pipes in suction or
pressure line are too small.
11
X
Check the coupling halves. They must be fixed
with 2-3mm space.
12
X
Check longitudinal play of coupling rod pins.
The spider might be worn.
13
X
X
X
Check whether foreign bodies in pump.
Disassemble pump, remove foreign bodies,
replace defective parts.
14 X
X
Pump stopped by the thermal circuit breaker.
Please allow the motor to cool down
– please
reduce the power consumption.
15 X
X
Bearings are worn or defective Disassemble
pump, replace the shaft
– bearing – cap unit
16
X
The valves are dry (e.g. not in use for a long
time), deformed or worn. Change valve or wet
the pump.
17
X
The diaphragm is burst ( the discharge pressure
was too high)
– replace pump chamber.
18
X
X
X
X
O
–rings between valve plate and pump housing
are defective.
19
X
Align coupling accurately
20
X
X
The clamping ring screw got loose
–fixe it!
